
export default function crweateFocusTrap({
  DATA_PREFIX,
  DATA_PREFIX_BASE,
  EventHandler,
  SelectorEngine,
  Config,
}) {
  /**
   * Constants
   */

  const NAME = 'focustrap'
  const DATA_KEY = `${DATA_PREFIX_BASE}.focustrap`
  const EVENT_KEY = `.${DATA_KEY}`
  const EVENT_FOCUSIN = `focusin${EVENT_KEY}`
  const EVENT_KEYDOWN_TAB = `keydown.tab${EVENT_KEY}`

  const TAB_KEY = 'Tab'
  const TAB_NAV_FORWARD = 'forward'
  const TAB_NAV_BACKWARD = 'backward'

  const Default = {
    autofocus: true,
    trapElement: null, // The element to trap focus inside of
  }

  const DefaultType = {
    autofocus: 'boolean',
    trapElement: 'element',
  }

  /**
   * Class definition
   */

  class FocusTrap extends Config {
    constructor(config) {
      super()
      this._config = this._getConfig(config)
      this._isActive = false
      this._lastTabNavDirection = null
    }

    // Getters
    static get Default() {
      return Default
    }

    static get DefaultType() {
      return DefaultType
    }

    static get NAME() {
      return NAME
    }

    // Public
    activate() {
      if (this._isActive) {
        return
      }

      if (this._config.autofocus) {
        this._config.trapElement.focus()
      }

      EventHandler.off(document, EVENT_KEY) // guard against infinite focus loop
      EventHandler.on(document, EVENT_FOCUSIN, (event) =>
        this._handleFocusin(event),
      )
      EventHandler.on(document, EVENT_KEYDOWN_TAB, (event) =>
        this._handleKeydown(event),
      )

      this._isActive = true
    }

    deactivate() {
      if (!this._isActive) {
        return
      }

      this._isActive = false
      EventHandler.off(document, EVENT_KEY)
    }

    // Private
    _handleFocusin(event) {
      const { trapElement } = this._config

      if (
        event.target === document ||
        event.target === trapElement ||
        trapElement.contains(event.target)
      ) {
        return
      }

      const elements = SelectorEngine.focusableChildren(trapElement)

      if (elements.length === 0) {
        trapElement.focus()
      } else if (this._lastTabNavDirection === TAB_NAV_BACKWARD) {
        elements[elements.length - 1].focus()
      } else {
        elements[0].focus()
      }
    }

    _handleKeydown(event) {
      if (event.key !== TAB_KEY) {
        return
      }

      this._lastTabNavDirection = event.shiftKey
        ? TAB_NAV_BACKWARD
        : TAB_NAV_FORWARD
    }
  }

  return FocusTrap
}
